1 66 The Evolution Hypothesis. 



be modified by the growth of new molecules; the 

 inter-molecular motions may be modi tied by the 

 inter-actions of each molecule and its environment ; 

 but no increase or diminution, or composition, or 

 variation of such motion will constitute that differ- 

 ence which exists between vital and mechanical action. 

 No change in the times of oscillation of the atomic 

 constituents or inter-action between molecular aggre- 

 gates and their environment will produce that which 

 is signified by the word life. Motions that are me- 

 chanical (or, if the term be preferred, dynamical) and 

 nothing more will not yield vital actions. 



It is not unusual for a disputant to cover a false 

 process in his logic by departures from sound reasoning 

 which escape detection from their apparent insignifi- 

 cance. Mr. Spencer's indiscernable modifications make 

 the contrast between life and the action of inorganic 

 matter less marked ; but we repeat, additions may 

 increase motion, variations may render it more complex 

 or change its direction or its mode, but no increase or 

 variation can make it other than dynamic. Minute 

 variations may insensibly change the physical action 

 or alter the chemical qualities of a portion of matter, 

 but can never bridge over the separation between the 

 dynamical and the vital. It is directly in the teeth 

 of all experience to deem it possible to divide and 

 subdivide life by little and little downward until 

 its distinctive characteristics have been pared away, 

 and it has become only a mode of molecular motion : 



